The advent of commercially available wide band digital communication links carries with it the ability to add new dimensions to the functions effected by a communication system. One aspect of these new dimensions is a teleconferencing function. In teleconferencing, conference participants are brought together via a communication link for the purpose of information interchange. The "tele" prefix to the word telecommunications implies that one or more of the participants is remotely located from other of the participants in the conference. Teleconferencing is a function which has been performed using prior art techniques and apparatus. Teleconferencing is achieved so as to give the perception that there is no distance barrier between participants who may actually be widely separated. This goal has not been achieved until the advent of this invention.
The prior art in teleconferencing can be broken down into two readily segregatible classes, those in which only audio information is interchanged, and those in which video information is interchanged as well. The first class of prior art techniques (audio information interchange only) has not been accepted as a viable alternative to bringing all the conference participants to a common site. In other words, while audio teleconferencing is a function which is carried out today, there are many instances in which it is not perceived to be an acceptable substitute to travel.
Other prior art methods and apparatus have added a video dimension to the teleconferencing function. These prior art approaches, too, have not been perceived as acceptable substitutes to actually bringing all participants to a common location. See "The Global Video Conference" by Mokhoff appearing in IEEE Spectrum, September 1980, pp 44-47. There appears to be two reasons for this perception. The first reason is that there has not been available to the prior art, the wide band communication facility which appears to be required for effective telecommunications. This problem appears to have been solved through the use of wide band communication links provided by domestic communication satellites and/or direct or line-of-sight microwave communication facilities. The other problem, however, still remains and it is the problem of equipment complexity. Effective telecommunication requires giving each participant the perception that there is no distance barrier between himself and each other conference participant. While this appearance was technically achievable using prior art methods and apparatus, it necessarily required plural TV cameras, each of which is capable of altering the image generated by varying parameters such as pan, tilt, zoom and focus. While the prior art could supply such equipment, that equipment necessarily required the presence of one or more equipment operators, who were technically trained to achieve the desired results. The cost associated with providing the operator(s) prohibited the widespread use of teleconferencing.
The prior art made several attempts to avoid this requirement for equipment operator(s). One attempt was by American Telephone and Telegraph Company. Their service used a combined television camera/video display unit. A user positioned himself in front of the equipment with two results. By reason of his position, the television camera generated a video image of the user which could be transmitted to other users. At the same time, the participant's presence in front of the equipment enabled him to view the video display which could produce an image of a distant user. In this regard see "Experiments with Picturephone Service" by A. D. Hall in the Bell Laboratories Record, April 1964, pp. 114 et seq; "New Picturephone Set `Zooms` and Shows Graphics" in Bell Laboratories Record, December 1967, pp. 374 et seq. This simple level of service was inadequate where a conference included more than two users; while equipment could be provided to select the video signal to be transmitted from one user's camera to the other displays, that equipment necessarily required an operator. Other prior art, as exemplified in U.S. Pat. Nos. 3,419,674; 3,723,653; 3,601,530; 3,725,587; 3,944,736 and 4,054,908, used plural TV cameras, each associated with a different field of view, and audio-driven majority voting logic to select from the set of TV cameras, the camera associated with a region including the highest audio source level. This approach too proved ineffective for a number of reasons; in the absence of an audio signal source, the system defaulted to a single camera which might or might not be trained on the image most desired by the participants. Secondly, unintentioned sounds (such as a cough or sneeze, etc.) could well cause a change in the video image being transmitted which was undesirable. Furthermore, no simple provision was made for changing a TV camera's field of view, i.e. pan, tilt, zoom and focus were not available. Some other approaches are referred to in "Teleconferencing Communications Activities" by Noll in Communications (September 1976), pp. 8 et seq.
Accordingly, it is an object of the present invention to provide a teleconferencing system enabling video teleconferencing which does not require the presence of skilled equipment operators, but which nevertheless has the capability of imparting to participants in a teleconferencing situation the perception of a lack of a distance barrier between participants who may actually be separated by great distances. It is another object of the present invention to provide such a system in which a conference leader, unskilled in the operation of the associated equipment, can nevertheless readily control the various components so as to generate this perception. It is still another object of the present invention to provide such a teleconferencing system in which an unskilled conference leader can control plural TV cameras so that a video image from a selected camera will be transmitted to a remote site, and who can also control the same camera in terms of pan, tilt, zoom and focus. It is another object of the present invention to allow an unskilled operator to effect the functions necessary to carry on a teleconferencing scenario and to select locally-generated images for transmission to a remote site so as to give the remote participants the perception of no distance barrier between themselves and other remotely located site(s).